‘Summer Queen’ passionfruit used in this study was collected from the Kagoshima Fruit Tree Experimental Station. As a result of analyzing the juice of the passionfruit using HPLC, it was found from the absorption spectrum that the main carotenoid in the passionfruit was z- carotene (Fig. 2). The UV-visible spectrum of z-carotene showed lmax at 379, 400 and 425, with high spectral fine structure (%III/II 93). After filtering the passionfruit juice on a Sep-Pak C18 cartridge, the concentration of ascorbic acid was rapidly and simply determined using the Reflectoquant Ascorbic Acid Test (Merck Ltd., Japan) without the need to use HPLC. The quantities of z-carotene and ascorbic acid in the passionfruit juice varied significantly according to harvesting season (Fig. 3). The concentrations of z-carotene and ascorbic acid were significantly higher in fruits harvested in autumn than in summer and winter. There was a direct correlation between z-carotene and ascorbic acid content (Fig. 4) that was not influenced by harvesting season, making it possible to estimate the concentration of z-carotene by measuring the concentration of ascorbic acid using the Reflectoquant Ascorbic Acid Test.
These results indicate that drip-fertigation and light culture is useful for harvesting autumn fruit that contains numerous functional contents.
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